The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As is visible on FIG. 1, in certain nacelles for dual-flow turbine engines, the rear part A, defining, with the fairing C of the turbine engine (often designated by “IFS”—or inner fixed structure”) the cold flow stream V, is exhibited in the form of a one-piece ferrule: in this case, it is usually called an “O-duct” type nacelle.
In this type of nacelle, the rear part of the nacelle A is slidingly mounted on an uppermost beam S by means of rails R, between the operating position visible on FIG. 1, and a maintenance position visible on FIG. 2, in which the rear part of the nacelle is moved to the rear of the nacelle, thus allowing access to the turbine engine T for maintenance work.
More particularly, once the rear part A has slid towards its downstream position visible on FIG. 2, the IFS C may be opened from the outside of the nacelle, by making the two halves which constitute it swivel around axes substantially parallel with the nacelle.
The sliding movement of the rear part of the nacelle towards its maintenance position may be achieved manually or by means of electrical or hydraulic actuators.
An example of such an actuator of the prior art is represented on FIG. 3.
As is visible on this figure, such an actuator comprises a worm drive 1 on which is screwed a nut 3, itself secured to an actuating tube 5 of which the free end ends by an eyelet or ball joint 7.
Preferably, balls 8 are interposed between the threads of the screw 1 and those of the nut 3, in such a manner as to reduce friction, such that this type of actuator is commonly called “ball screw”.
The screw 1 comprises, at the end opposite that of the ball joint 7, a pinion 9 with oblique toothing cooperating with a master pinion 11 itself directly or indirectly driven by an electrical engine.
Under the action of this electrical engine, the screw 1 may be swiveled in one direction or the other, and thus translate the nut 3 in one direction or the other, and hence elongate or retract the tube 5.
These movements of the tube 5 allow, by means of the ball joint 7, to act on the rear part of the nacelle A.
As it may be understood, when such an actuator is in complete extension position, its cantilever is very important, namely substantially equal to twice the length of the screw 1.
Apart from the fact that such a cantilever may generate significant friction, or even, blocking particularly the nut 3 with respect to the screw 1, it requires an important dimensioning of the different pieces (screw 1, nut 3, tube 5) in order to provide sufficient resistance to buckling forces; such a dimensioning leads to excess weight.